As a conventional technology of this sort, there is one disclosed in Patent Document 1. Disclosed in this Patent Document 1 is a construction that, to avoid freezing of a liquid reducing agent for reducing nitrogen oxides emitted from an engine, a liquid reducing agent tank is arranged in a vehicle or machine, for example, in a hydraulic excavator at a position where it can be kept warm. Described specifically, a construction is disclosed, in which the liquid reducing agent tank, in other words, the reducing agent storage tank is arranged at a position where it can be kept warm, such as in close proximity to a hydraulic pump or in close proximity to a valve, i.e., a hydraulic pressure control valve unit in an engine compartment, in an operator's cab, or in close proximity to a a hydraulic oil tank.
Patent Document 1: JP-A-2003-20936